One of the most serious concerns with vehicles powered by internal combustion engines is the creation of pollution. This presents such a serious problem that pollution control has become by law a necessity in, for example, permitting a vehicle to pass state inspections. Various attempts have been made to provide pollution control devices. These efforts have had limited and varying success.
Crankcase emissions were the first target of law makers and automotive engineers because one-third of the engine emissions originate from this point. Since 1968 and to the present, the PCV system was the standard crankcase ventilation method used on all domestic and foreign cars. The PCV system removes engine crankcase vapor resulting from normal engine blow by-unburned fuel and combustion products leaking past the rings into the crankcase. Manifold vacuum draws fresh air through the crankcase which pulls the undesirable corrosive gases and unburned fuel into the manifold so that they can be burned in the engine. When the PCV valve is open air flows through the air cleaner into the crankcase where it picks up vapor, then into the intake manifold.